The magnetotropic susceptibility emerges naturally in frequency shift measurements.[1]}, [2]}, [3]}, [4]}, [5]}, [6]} In these measurements, the sample is attached to the tip of a freely oscillating cantilever. The cantilever-sample assembly can be driven near its mechanical resonance by a piezo-mechanical transducer (or optical pressure[5]}). Its mechanical response can be read out in a similar way. When driven near one of its mechanical resonances, the cantilever behaves as a simple harmonic oscillator with mechanical energy
\(E= \frac{I}{2} \left(\frac{dΔθ}{dt}\right)^2 + \frac{K}{2} Δθ^2 \,.\) 
